1. Field of the Invention
The present invention relates to a phase comparator circuit, more particularly, to a phase comparator circuit for comparing the phases of two input signals and outputting two output signals in accordance with the result of the comparison.
2. Description of the Related Art
A phase comparator circuit, for example, is used in a PLL (phase-locked loop) circuit, which compares the phases of two input signals and outputs two output signals in accordance with a phase difference between the two input signals of the phase comparator circuit. A conventional phase comparator circuit is designed to obtain an ideal characteristic in the two output signals thereof. In this ideal characteristic, when a phase difference occurs between the two input signals, the two output signals are not output, and thus the level of both output signals is made a logical low level.
However, generally speaking, a manufactured conventional phase comparator circuit does not have the above ideal characteristic, due to dispersions of the elements or parts of the phase comparator circuit, and thus a problem arises in the PLL circuit using such a conventional phase comparator circuit in that the two output signals thereof are not output when the two input signals are in-phase. The problem of the conventional phase comparator circuit will be later explained in detail.